The present invention relates to an improvement of device for adjusting a clearance of a twin clutch, as dislcosed in U.S. patent application Ser. No. 791,825, filed on Oct. 28, 1985, now U.S. Pat. No. 4,684,002, dated Aug. 4, 1987, and assigned to the assignee hereof, in which two clutch disks are disposed with an intermediate plate therebetween.
In a known twin clutch, shown in FIG. 6, two clutch disks 3 and 4 are disposed between a flywheel 1 and a pressure plate 2 with an intermediate plate 5 therebetween. These members are of annular shape and are disposed concentrically to an output shaft 6, only a center line of which is illustrated, respectively. The clutch disks 3 and 4 are provided at the radially outer portions with friction facings 8 and 9, and are connected at radially inner hubs to the output shaft 6, respectively. An engaging-releasing mechanism (now shown), such as a diaphragm spring, is connected to the pressure plate 2. In the engaging operation of the clutch, said mechanism forces the pressure plate 2, so that the pressure plate 2 presses the facings 8 and 9 against the flywheel 1 and the intermediate plate 5.
The intermediate plate 5 is provided with a plurality of outer peripheral projections 15. Each projection 15 is provided with a hole 16 parallel to the output shaft 6. A stopper pin 17 is fitted into the hole 16.
As shown in FIG. 7, each stopper pin 17 is formed by a cylindrical spring member having one axially extending slit 17a, and is elastically compressively fitted into the hole 16. The projections 15 are connected to a flywheel ring 19 through elastic straps 18, so that the intermediate plate 5 is biased in a clutch disengaging direction D, shown in FIG. 6, by the straps 18. The flywheel ring 19 is integrally formed with the flywheel 1, and is arranged at the opposite side to the flywheel 1 with the projections 15 therebetween.
In the illustrated clutch engaged condition, the stopper pins 17 contact the flywheel 1, and an axial space L is formed between each stopper pin 17 and the flywheel ring 19.
According to the above structure, when the pressing force by the pressure plate 2 to the facing 9 is released, the facing 9 moves away from the pressure plate 2 and the intermediate plate 5, and the intermediate plate 5 is moved in the disengaging direction D by the elastic straps 18 to release the pressing force applied against the facing 8, so that the clutch disengages.
In this operation, the intermediate plate 5 moved in the direction D stops at a position at which the stopper pins 17 contact the flywheel ring 19, so that the intermediate plate 5 does not move excessively toward the pressure plate 2. Therefore, in the disengaging operation, the intermediate plate 5 is not pressed to the facing 9, and thus, a torque is not transmitted through the intermediate plate 5 and the clutch disk 4 to the output shaft 6.
When the facing 8 wears to some extent after a long use, the position of the intermediate plate 5 in the engaged condition moves toward the flywheel 1. In this case, after the stopper pins 17 contact the flywheel 1, the intermediate plate 5 is further forced by the pressure plate 2, and thus, a sliding occurs between the inner peripheral surfaces of the hole 16 and the stopper pins 17, so that the intermediate plate 5 moves in an engaging direction E with respect to the stopper pins 17.
However, in the above structure, there is a relatively large resistance between the inner surfaces of the holes 16 and the stopper pins 17 when the intermediate plate 5 moves in accordance with the wear of the facing 8, so that the pressing force applied from the plate 2 through the intermediate plate 5 to the facing 8 is reduced by the above frictional resistance. Therefore, it is difficult to press the facing 8 onto the flywheel 1 by a sufficiently large force, and thus, it is difficult to transmit a sufficiently large torque from the flywheel 1 to the clutch disk 3.
Further it is difficult to accurately set or adjust the frictional force between the inner surfaces of the holes 16 and the stopper pins 17 at an intended value. If the frictional force is too small, there is such a problem that the intermediate plate 5 moves in the disengaging direction D and is pressed to the facing 9 during the disengaging operation, even after the stopper pins 17 contact the flywheel ring 9. If the frictional force is too large, said problem, i.e., the reduction of the pressing force for the facing 8 in the engaging operation, becomes remarkable.
The above problem can be solved by employing one-way clutch mechanism as disclosed, e.g., in U.S. Pat. No. 3,360,089, in which a combination of spring washers and pins are used for adjusting the clearance.
However, in this structure, only one washer of merely annular shape is associated to each pin, and thus, only axially one portion of each pin is engaged with the washer, so that relatively large engaging force is generated in the engaged portions of the washer and the pin. Therefore, after a long use, it may be impossible to obtain an intended engaged condition due to the wear of the engaged portions.
Further, it is necessary to form recesses in the pressure plate for accomodating the washers and to fix auxiliary plates to the pressure plate for closing the recesses and holding the washers, which complicates the structures.
Accordingly, it is an object of the invention to provide an improved structure, overcoming the above-noted disadvantages.